1. Field of the Invention
The present invention relates to an apparatus for cooking by heating of the type in which a heat source is switched on and off by a microcomputer in accordance with the detected level of a cavity temperature controlling sensor. The cavity temperature is prevented from exceeding a given temperature thereby heating an object at a desired temperature, and making it possible to provide the optimum finish to prepared confections such as cakes and cookies whose temperature control is not easy.
2. Description of the Related Art
Due to the recent popularization of apparatus for cooking by electric heating such as ovens/ranges, the making in the home of confections such as cakes, cookies and chous (a cream puff) in an oven has been increasing in frequency. In addition, due to the recent liking for gourmet foods, importance has been attached to the finish of food and the speed-up of cooking time.
However, the cooking of such cakes, cookies, chous, etc., is sensitive to heating temperature and therefore there has been a tendency for their finish to be greatly deteriorated if a given baking temperature is exceeded (this phenomenon is hereinafter referred to as an overshooting). The reason is that when overshoot occurs, the food is baked at a temperature higher than its essential optimum baking temperature so that the surface of the food is baked first and its water content is not taken up, thereby cooking the food rather rare.
To prevent such overshoot, it has been the usual practice in the past to preheat the oven until the inner temperature of the heating chamber attains the desired baking temperature before an object to be heated is placed inside the heating chamber (This operation is hereinafter referred to as a preheating operation).
However, the preheating requires considerable time and also energy is wasted. In addition, there is another disadvantage that even though the preheating is effected, if the placing of the object inside the heating chamber takes time, the internal temperature of the heating chamber drops thereby causing overshoot.
As a countermeasure, a method has been proposed which eliminates the preheating to prevent any over-shoot. This method is so designed that in addition to a conventional first sensor for detecting the temperature in the heating chamber to control the on-off operations of a heater, a second sensor is mounted near the heater to detect the temperature of the heater itself to compensate for the delay in the thermal response of the conventional sensor, thereby eliminating the occurrence of overshoot.
However, this construction has the following disadvantages. Firstly, the second sensor must be arranged in the vicinity of the heater and therefore it must have an excellent high temperature characteristic thus making it quite expensive. Another disadvantage is that the second sensor must be brought into complete close contact with the heater thus requiring a complicated mounting structure and deteriorating the mounting performance. Still another disadvantage is that the construction tends to be subjected to the effect of external air, the heat of a lamp for illuminating the interior of the heating chamber, etc. In addition, although having an excellent high temperature characteristic, the second sensor or thermistor is not suited for the control of the heating chamber temperature and its use along with the conventional thermistor results in an increase in cost.